Woocommerce Avatax Customization

Hi! I currently use Avatax for a client and need someone to build a plugin that extends the Avatax Woocommerce plugin. Currently, the plugin uses the Woocommerce Email address as the Avatax Customer ID. To sync correctly with users in our Netsuite ERP, I need to be able to override that with the use of a custom customer field in Woocommerce to relate to the customerid in Avatax.